1. Field of the Invention
The present invention relates to new creping adhesives and more particularly it relates to polyakanolamide tackifiers obtained from the condensation of polycarboxylic acids with alkanolamines.
2. Description of the Prior Art
Alkanolamides prepared from the reaction of alkanolamines with monofunctional long chain fatty acids have been described in the patent literature. The earliest example is of the alkanolamide obtained from a 2:1 molar mixture of alkanolamine and fatty acid described in 1937 by W. Kritchevsky in U.S. Pat. Nos. 2,089,212 and 2,096,749. These are low purity, water-soluble products that contain high levels of unreacted alkanolamine. The water solubility is a direct result of the presence of the large amounts of unreacted alkanolamine. This type of material has found utility as a component of surfactant formulations.
Another type of alkanolamide composition has been described in the patent literature that is prepared by reacting equimolar amounts of a fatty acid ester with an alkanolamine to yield a higher purity alkanolamide. E. M. Meade, U.S. Pat. No. 464,094; G. C. Tesoro, U.S. Pat. No. 2,844,609; J. V. Schurman, U.S. Pat. No. 863,888. These compounds are not water soluble by themselves. They can be rendered soluble in water by combining them with an anionic or nonionic surfactant. These alkanolamides are also useful in surfactant formulations.
A number of water-soluble adhesive compositions used in the creping process have been described in the patent literature. Canadian patent No. 979,579, U.S. Pat. No. 5,338,807, U.S. Pat. No. 4,075,177, U.S. Pat. No. 3,640,841 and U.S. application Ser. No. 08/1428,287, filed Apr. 25, 1995, all describe water-soluble polyamidoamine-based compositions that function as adhesives for the creping process in papermaking. Other patents such as U.S. Pat. No. 4,501,640, U.S. Pat. No. 4,584,439, U.S. Pat. No. 4,788,243, U.S. Pat. No. 4,528,316 and U.S. Pat. No. 5,179,150 describe mixtures of poly(vinyl alcohol) and polyamide polymers that are useful as creping adhesives.
Tackifying resins are an essential component of rubber-based adhesives. "Kirk-Othmer Encyclopedia of Chemical Technology", 3rd Ed., Vol 1, pp. 509 & 510 and Kirk-Othmer Encyclopedia of Chemical Technology", 3rd Ed. Vol. 13, pp. 347 & 348. These tackifiers are hydrocarbon materials based on rosin esters, terpene resins (poly .alpha.- and .beta.-pinene), petroleum-derived resins made from C.sub.5 and C.sub.9 feedstocks, coumarone-indene resins and copolymers of .alpha.-methylstyrene and vinyltoluene. These are hydrocarbon-based, hydrocarbon-soluble materials that are typically used with hydrocarbon-based, hydrocarbon-soluble rubbers such as natural rubber and styrene-butadiene rubber (SBR). The tackifying resins function by modifying the viscoelastic properties of the rubber adhesive that they are blended with. D. W. Aubrey & M. Sherriff, J. Poly Sci.: Poly Chem. Ed., 16, pp. 2631-2643 (1978).
U.S. Pat. No. 2,396,248 discloses a process for making polymers comprising heating at a temperature below 180.degree. C. a reaction mixture comprising essentially bifunctional reactants comprising monoaminomonohydric alcohol and a dibasic carboxylic acid, heating the low molecular weight polymer at polymerizing temperatures until a polymer is formed which can be formed into pliable filaments, the carboxylic groups in the mixture of bifunctional reactants being present in an amount substantially equimolecularly equivalent to the sum of the amino and alcoholic hydroxyl groups. The polymers produced by this process are disclosed to have great strength, toughness, flexibility and elasticity and good fiber forming and cold drawing properties.
U.S. Pat. No. 2,386,454 discloses a microcrystalline linear polymer having permanent molecular orientation produced by the application of directional stress to the reaction product produced by condensing by heating a mixture including a monoalkylolamine which has at least one hydrogen atom attached to the hydrogen atom and an aliphatic carboxylic acid which has at least three carbon atoms between the carboxyl groups, under polymerizing conditions until substantially completely reacted, the carboxyl groups in the mixture being present in an amount substantially equimolecularly equivalent to the sum of the amino and alcoholic hydroxyl groups, and which reaction product is capable of being cold drawn into fibers exhibiting molecular orientation along the fiber axis. The polymers so obtained are disclosed to be suitable for coating, impregnating or fiber-forming purposes having high strength and elasticity.